Bug 909974 - Add a hang monitor for background threads; r=froydnj
Bug 909974 - Let monitor thread detect hangs in addition to permahangs; r=froydnj
Bug 909974 - Stop the monitor thread when the BackgroundHangManager instance is destroyed; r=froydnj
Bug 932865 - Add ThreadHangStats for collecting background hang telemetry; r=vladan
Bug 935092 - Const-ify profiler pseudostack entries; r=BenWa
Bug 935092 - Add ThreadStackHelper to get a thread's pesudo-stack; r=BenWa
Bug 932865 - Add way for telemetry to iterate over active threads; r=froydnj
Bug 932865 - Record inactive thread hang stats inside telemetry; r=vladan
Bug 932865 - Expose thread hang stats through nsITelemetry and telemetry ping; r=vladan
Bug 932865 - Collect thread hang stats in BackgroundHangMonitor; r=froydnj